Pressure jet burner control systems

ABSTRACT

THE INVENTION RELATES TO PRESSURE JET BURNER CONTROL SYSTEMS INCLUDING A MOTOR DRIVEN FUEL PUMP WHICH STOPS AND STARTS ACCORDING TOE TH EFUEL REQUIREMENTS OF THE BURNER AND IN WHICH CUT-OFF AND START-UP OF THE FUEL SPRAY IN THE BURNER IS ADRUPT AND THE PRESSURE OF FUEL IS MAINTAINED ABOVE A PREDETERMINED MINIMUM PRESSURE OF THE VOLUME. FUEL SUPPLY TO THE BURNER IS CONTROLLED BY A QUICK CUT-OFF VALVE ARRANGED TO START AND CUT OFF FUEL AT PREDETERMINED FUEL PRESSURE AND ALSO INCLUDES A BY-PASS LINE CONNECTED IN THE FUEL LINE BETWEEN THE CUT-OFF VALVE AND THE PUMP, AID BYPASS LINE BEING CONTROLLED BY A SOLENOID VALVE WHICH SIMULTANEOUSLY RELIEVES FUEL TRAPPED IN SAID FUEL LINE UNDER PRESSURE WHEN THE FUEL PUMP IS DEENERIGISED.

p 20, 1 I E. PRITCHARD 3,605,158

, PRESSURE JET BURNER CONTROL SYSTEMS Filed Nov. 13, 1969 I /llI'JDWAIU) I'IHTCHIUU), LIN -n")! Attorneys United States Patent Int. Cl.1304b 9/ F02g 3/00; F0411 9/00 US. Cl. 239-124 Claims ABSTRACT OF THEDISCLOSURE The invention relates to pressure jet burner control systemsincluding a motor driven fuel pump which stops and starts according tothe fuel requirements of the burner and in which cut-off and start-up ofthe fuel spray in the burner is abrupt and the pressure of fuel ismaintained above a predetermined minimum pressure of the volume. Fuelsupply to the burner is controlled by a quick cut-off valve arranged tostart and cut off fuel at predetermined fuel pressure and also includesa by-pass line connected in the fuel line between the cut-off valve andthe pump, said bypass line being controlled by a solenoid valve whichsimultaneously relieves fuel trapped in said fuel line under pressurewhen the fuel pump is deenergised.

This invention relates to pressure jet burner control systems and inparticular relates to burner systems comprising motor driven fuel pumpswhich stop and start according to the fuel requirements of the burner.With systems of this type, it is important that cut-off and startup ofthe fuel to the burner be abrupt so that any fuel flow through theburner should be above a predetermined minimum pressure and volume.

If fuel begins to flow through the burner at low pressure, then a poorspray of fuel issuing from the burner nozzle will result to cause poorstarting thereof and inefiicient burning of fuel. Furthermore withexisting systems, it has proved difficult to overcome the problem of jetnozzle dribble after the fuel pump has been tie-energised in that in apractical situation, it is impossible for the fuel pump to immediatelycease pumping. Many systems are in use, all of which do not completelyovercome the abovementioned problems, and those that do, must contendwith new problems inherent in their construction.

A control system is known utilising a solenoid fuel valve near the jetnozzle and adapted to open when the burner is energised, and close whenthe burner is de-energised. With this system, starting of the burner canbe poor in that it opens immediately the burner is energised wherebyinitial fuel fiow is at lower than optimum pressures. Furthermore,because of its electrical operation, overheating of the solenoid fuelvalve must be avoided and thus it cannot be placed close to the jetnozzle to minimize fuel dribble caused by residual fuel in the lines.

A simple mechanical sharp cut-off valve is also known comprising aspring loaded diaphragm, plunger or valve installed between the fuelpump and the jet nozzle and is arranged to cut off fuel at apredetermined fuel pressure less than the optimum fuel pressure.However, since the fuel pump is unable to immediately stop pumping uponshut off, the cut-off valve is unable to stop all fuel pumped to theburner until the pump slows sufficiently so that all pumped fuel can beleaked back through the system.

Before this takes place, the action of the cut-off valve can be to takeup a steady or unsteady throttling position which does not act to cutoff the fuel sharply as desired.

A control system which uses a mechanical valve and a solenoid fuel valvein series between the fuel pump and the jet can suffer in practice fromthe fault that, on shut down, fuel can be trapped in the pipelinebetween the two valves. On re-start, when the solenoid valve is last inline, the burner may be relit due to the release of the trapped fuel butat an undesirably low fuel pressure. This action can take place beforefuel begins to arrive from the fuel pump and through the mechanicalvalve. Alternatively, when the mechanical valve is last in line, weepingof fuel at the jet can take place after shut off 1f the pressure oftrapped fuel increases for any reason.

The problem of trapped fuel can be overcome by the fitting of a fuelline containing a one way valve which can lead the otherwise trappedfuel back to the delivery side of the fuel pump. This is an undesirableadditional complication.

In general, the action of a solenoid shut-off fuel valve can be upset bythe inertia of the fuel in the pipelines which may cause bouncing of thevalve on its seat.

It is an object of the present invention to provide an improved pressurejet burner control system in which the abovementioned disadvantages andcomplications are overcome.

With the above objective in view, there is provided according to thepresent invention a pressure jet burner control system comprising a fuelpump, a burner, a fuel line connecting said pump and burner, a burnervalve including a plunger acting in cooperation with a seat disposed insaid fuel line, said plunger being biased toward said seat to preventfuel under a predetermined minimum pressure to flow to said burner, afuel line for by-passing said pump connected into said fuel line betweensaid pump and said burner valve, and a by-pass valve adapted toinstantly close and open upon respective energisation andde-energisation of said fuel pump and disposed in the by-pass line,whereby upon said fuel pump being deenergised, pressure between saidburner valve and said pump is instantly relieved through said by-passline.

Conveniently, the by-pass valve includes a solenoid actuated needleplunger acting in cooperation with a seat opening to prevent passage offuel in the by-pass line when the solenoid winding is energised. Theneedle plunger is biased by spring means towards an open valve position.Preferably, the by-pass fuel line is situated near the burner valve tominimise the effect of fuel hammer caused by inertia of fuel in thelines upon shutting of said burner valve. It has been found that theeffects of fuel inertia is also serious where the fuel shut off valve isnot adjacent the burner jet nozzle. The fuel inertia causes fuel tocontinue flowing out of the nozzle even after cut-off by the valve.

The burner valve needle plunger is spring biased to close against saidseat. The pressure of fuel flowing in said fuel line is adapted to acton a diaphragm connected to said needle plunger to compress said biasingspring and thereby move said needle plunger away from its seat and allowfuel flow to burner.

In order that the construction of the control system of the inventionmay more readily be understood, reference will be made to a practicalarrangement as hereinafter described having reference to theaccompanying drawing. The arrangement can be used in any externalcombustion application and particularly in a steam engine where the fuelpump is continually switched on and off according to requirements of theengine boiler.

The system includes a source of fuel 1, a pump 2, a burner jet body 3 inwhich a burner fuel valve 4 is preferably integrally mounted. Thisensures that the valve is arranged closely adjacent to the burner jet3a, thus minimizing the effects of fuel inertia in the passage betweenthe burner valve and the burner jet. A burner motor 5, energized bybattery 30 and controlled by switch means 31, driving said pump 2 and anair fan 6 connected to the air register (not shown) supplying air to theburner. The burner valve 4 includes a needle plunger 7 biased toinstantly close against seat 8 by spring 9, the spring bias beingadjustable by screw nut 10 to set the valve to a predetermined minimumfuel pressure, the valve including a fuel and air impervious diaphragm11 upon which said plunger 7 is mounted for movement between an open andclosed position. The plunger 7 is surrounded by a follower spring 7awhich ensures that the plunger 7 follows movement of the diaphragm 11.Connected into the fuel line 12 between the pump and the burner valve isa by-pass line 13 leading back to the fuel source 1 and in which isdisposed a solenoid actuated valve including a needle plunger 21. Valveplunger 21 is arranged with a quick-acting means disposed to constantlybias the valve plunger to the open position, for example biased by aspring 22 to an open valve position off seat 23. The armature 24 of thesolenoid bypass valve 20 is adapted to act against and overcome saidspring bias so as to close said seat opening. The winding 25 of thesolenoid valve is connected into the electrical circuit, includingbattery and switch means 31, of the burner motor 5 or alternatively isarranged to be energised and de-energised simultaneously upon startingand stopping respectively of the fuel pump 2. It will be understood thatthe simultaneous control of the fuel pump 2 and solenoid valve 20 can becarried out in many ways and this practical arrangement should not beconstrued as limiting on the present invention in its more generalforms.

In operation of this arrangement, the burner motor 5 is energised todrive the air fan 6 and fuel pump 2, and simultaneously the solenoidwinding 25 is energised to force the armature 24 to instantly move theneedle plunger 21 of said solenoid actuated by-pass valve 20 to a closedposition. Upon closure of said valve, fuel pressure in the line 12 tothe burner valve 4 increases until the force exerted on the valvediaphragm 11 is greater than that exerted by said biasing spring 9acting in opposition thereon whereby the plunger 7 moves to an openposition to allow fuel to flow to the burner jet 3a. This conditionindicates that the pressure of fuel has reached an acceptable minimumpressure for efficient atomisation and burning in the combustion spacesurrounding the burner 3. The force of the biasing spring 9 can bevaried to arrive at an acceptable minimum pressure.

Upon stopping of the fuel pump 2 as by switching off the burner motor 5by a thermostat boiler pressure switch or similar means 31 as shownschematically in the drawing, the winding 25 of said solenoid valve 20is simultaneously de-energised whereby the needle plunger 21 thereof islifted instantly from its seat by spring 22 to relieve the pressurisedfluid in said fuel line 12 back to said fuel source 1 and in turn saidburner valve 4 is closed rapidly through drop in fuel pressure toprevent any undesirable low pressure flow of fuel to the burner 3. Theshort distance between the seat 8 and the burner jet 3a in the burnerbody ensures that only a relatively small amount of fuel remains at theburner jet and accordingly fuel dribble at cut-off, and the effects offuel inertia are at a minimum. Also since the solenoid valve is openedimmediately the fuel pump is stopped, fuel pressure is relieved frombehind the plunger 7 and the plunger will quickly close. The plunger 7will not lift off the seat 8 until sufficient fuel pressure is built upon the diaphragm 11 when pumping is recommenced. Thus sharp cut-01f andstarting of fuel flow to the burner jet is obtained by the presentinvention.

I claim:

1. A pressure jet burner control system comprising a fuel pump, aburner, a jet nozzle in said burner, a fuel line connecting said pumpand burner, a burner valve including a plunger acting in cooperationwith a seat opening disposed in said fuel line closely adjacent to saidburner nozzle, said plunger being biased by quick-acting means towardsaid seat opening to close said burner valve instantly to prevent fuelunder a predetermined minimum pressure to flow to said burner jetnozzle, a fuel line bypassing said pump connected into said fuel linebetween said pump and said burner valve, and a by-pass solenoid valvehaving a valve opening and disposed in theby-pass line, switch meansarranged in an electric circuit to control energisation andde-energisation of said fuel pump and said solenoid valve, the solenoidvalve being adapted to close and open its valve opening simultaneouslyupon respective energisation and de-energisation of said fuel pump, sothat upon said fuel pump being de-energised, pressure between saidburner valve and said pump is relieved instantly simultaneously throughsaid by-pass line, so that all of the by-pass line fuel passes throughsaid bypass solenoid valve opening upon the opening thereof.

2. A pressure jet burner control system as claimed in claim 1 whereinsaid hy-pass solenoid valve includes a solenoid actuated needle plungerco-operable with a seat type opening to prevent passage of fuel in thebypass line when the solenoid Winding is energised.

3. A pressure jet burner control system as claimed in claim 2 whereinsaid by-pass solenoid valve includes quick-acting spring means forbiasing its needle plunger towards an open valve position, and thesolenoid is arranged so that upon being energised it compressinglyopposes said spring means and holds said by-pass valve needle plungerclosed in its seat opening, and upon deenergisation releases said springto effect quick opening of said by-pass valve seat opening to permitsaid by-pass fuel to pass therethrough.

4. A pressure jet burner control system as claimed in claim 1 whereinsaid burner includes quick-acting spring means cooperable with saidvalve needle plunger to spring bias it to close against said seat sothat the pressure of fuel flowing in said fuel line is adapted to act ona diaphragm operably connected to said plunger tending to compress saidbiasing spring means and thereby move said needle plunger away from itsseat and allow fuel flow to said burner jet.

5. A pressure jet burner control system as claimed in claim 1 whereinsaid burner valve is integrally mounted in said burner.

References Cited UNITED STATES PATENTS 1,263,654 4/1918 Doble 137-5633,073,115 1/1963 Cowles et al. 6039.28 3,390,522 7/1968 Whitehead60-3928 ROBERT M. WALKER, Primary Examiner US. Cl. X.R.

